SQL 查詢未在 SUM 和 COUNT 中找到所有行

Question

select coalesce(ratings.positive,0) as positive,coalesce(ratings.negative,0) as negative,articles.id,x.username,commentnumb, 
    articles.category,
    articles."createdAt",
    articles.id,
    articles.title,
    articles."updatedAt"
    FROM articles
    LEFT JOIN (SELECT id AS userId,username,about FROM users) x ON articles.user_id = x.userId
    LEFT JOIN (SELECT id,
        article_id,
        sum(case when rating = '1' then 1 else 0 end) as positive,
        sum(case when rating = '0' then 1 else 0 end) as negative
        from article_ratings
        GROUP by id
        ) as ratings ON ratings.article_id = articles.id
    LEFT JOIN (SELECT article_id,id,
       count(article_id) as commentNumb
       from article_comments
       GROUP by id
       ) as comments ON comments.article_id = articles.id
    WHERE articles."createdAt" <= :date
    group by ratings.positive,ratings.negative,articles.id,x.username,commentnumb
    order by articles."createdAt" desc
    LIMIT 10

代碼正在運行，但是我的評論和評分比 SUM 和 COUNT 函數中計算的要多得多。

如何修復此查詢？

這是使用 postgres。

我做了一些實驗，似乎第三個評論加入是引起問題的一個。

Answer 1

在派生表中，理想情況下您應該使用 article_id 進行分組。 但是，您是根據 id 分組的。 因此，您在派生表中獲得的行數超過了必要的行數。 我已修改查詢以滿足您的需要。

    SELECT COALESCE(ratings.positive,0) AS positive,COALESCE(ratings.negative,0) AS negative,articles.id,x.username,commentnumb, 
        articles.category,
        articles."createdAt",
        articles.id,
        articles.title,
        articles."updatedAt"
        FROM articles
        LEFT OUTER JOIN (SELECT id AS userId,username,about FROM users) x ON articles.user_id = x.userId
        LEFT OUTER JOIN (SELECT article_id,
            SUM(case when rating = '1' then 1 else 0 end) as positive,
            SUM(case when rating = '0' then 1 else 0 end) as negative
            FROM article_ratings
            GROUP by article_id 
            ) AS ratings ON ratings.article_id = articles.id
        LEFT OUTER JOIN (SELECT article_id,
           count(article_id) as commentNumb
           FROM article_comments
           GROUP by article_id
           ) AS comments ON comments.article_id = articles.id
        WHERE articles."createdAt" <= :date
        ORDER BY articles."createdAt" desc
        LIMIT 10;